Ink-jet recording media comprising a radiation-cured coating layer and a continuous in-line process for making such media

ABSTRACT

Ink-jet recording media and continuous in-line process for manufacturing such media are provided. The media can be printed with ink-jet printers to form images having good color density, brilliance, and resolution. The ink-jet recording media include a paper substrate coated on one surface with a radiation-curable composition and an ink-receptive composition. The back surface of the paper may be coated with a polymeric coating to reduce curl and improve dimensional stability. The media have a water vapor transmission rate of no greater than 12 grams/100 square inches/24 hours and preferably have a surface gloss of at least 70.

BACKGROUND

[0001] 1. Technical Field

[0002] This invention relates to imaging media suitable for use withink-jet printers. More particularly, the invention relates to ink-jetrecording media comprising a paper substrate coated on one surface witha radiation-curable composition and an ink-receptive composition. Theother surface of the paper may be coated with a polymeric coating toimprove the paper's dimensional stability. The invention alsoencompasses a continuous in-line process for making such imaging media.

[0003] 2. Brief Description of the Related Art

[0004] Today, individual consumers and businesses are turning to ink-jetprinting systems and digital technology to produce many differentimaging media products. With the introduction of new computers,software, and digital cameras, consumers are now able to create greetingcards, posters, calendars, newsletters, fliers, window decals and thelike in the comfort of their own homes. Companies can create smallformat products such as business cards, company newsletters, brochures,promotional materials, overhead transparencies, and the like. Companiescan also create large indoor and outdoor advertising displays and othergraphic art materials for business presentations.

[0005] In an ink-jet printing process, liquid ink is squirted throughvery fine nozzles in a printer. The resultant ink droplets form an imagedirectly on a recording medium that typically comprises a coated film orpaper substrate. The quality of the final image or text is partlydependent on the composition of the ink-jet recording mediumparticularly the coating(s) and substrate. The inks used in most ink-jetprinters are aqueous-based inks containing molecular dyes or pigmentedcolorants. Water is the major component in aqueous-based inks. Smallamounts of water-miscible solvents such as glycols and glycol ethersalso may be present. Other ink-jet inks are non-aqueous based inkscontaining organic vehicles (e.g., hydrocarbon solvents) as the majorcomponent.

[0006] “Photo-papers” are particularly popular, because a person canproduce photographic-like images on these materials. Paper substrates,e.g., plain papers, clay-coated papers, and polyethylene resin-coatedpapers, can be used to make photo papers. The paper substrate is coatedwith specially formulated coatings that are capable of receivingaqueous-based inks from ink-jet printers.

[0007] Often, the substrate is a polyethylene-coated paper. Such paperscan have good dimensional stability and moisture resistance. Thepolyethylene coating acts as a moisture-barrier layer helping to preventthe aqueous ink vehicle from permeating into the base paper.Polyethylene-coated papers are commercially available from Jen-Coat,Inc. (Westfield, Mass.) and other companies under various trademarks.However, there are some disadvantages with using polyethylene-coatedpapers, including their manufacturing costs and thermal stability. Forexample, it may be difficult to use polyethylene-coated papers in hightemperature manufacturing operations, such as those where additionalcoating layers must be dried, because of polyethylene's thermoplasticproperties. Further, some polyethylene-coated papers tend to have lowsurface gloss which may be undesirable for some commercial applications.As an alternative, clay-coated papers can be used. The cost ofclay-coated papers is generally lower. But, clay-coated papers tend toabsorb the aqueous ink vehicle and this absorption may lead to curlingof the paper's edges and cockling of the paper's surface.

[0008] D'Anna et al., U.S. Pat. No. 5,800,884 discloses a gloss coatingcomposition comprising radiation curable oligomers and monomers, andphotosensitizers. The coating composition is applied to at least onesurface of a substrate and exposed to an ultraviolet light sourceresulting in curing of the composition onto the substrate's surface. Thepatent discloses that the coating can be applied to non-woven, woven,synthetic paper, paper, paperboard, plastic, or metal substrates. Thepatent further discloses that the coating composition can be used asprimer coat over a substrate's surface, wherein the coating surface iscapable of printing with ultraviolet or ultraviolet compatible inks.Alternatively, or in addition, to the primer coat, the coatingcompositions are used as a top coat over a substrate surface to impartgloss characteristics, good rub resistance, and flexibility to thesubstrate.

[0009] Nowak, U.S. Pat. No. 4,265,976 discloses an ultravioletradiation-curable coating composition comprising (1) chlorinated rubber,(2) chlorinated paraffin, (3) vinyl acetate, (4) trimethylolpropanetriacrylate, (5) photoinitiator, and (6) heat and light stabilizers forthe chlorocarbon components. The patent discloses that the coating hasutility as a moisture-barrier film for the protection of substrates suchas paper and cardboard. For example, the patent discloses the coatingsystem can provide a moisture-barrier coating on detergent boxes in asingle coat procedure.

[0010] Mehta et al., U.S. Pat. No. 5,219,641 discloses using aradiation-curable coating on certain substrates to make them receptiveto images from a thermal transfer printer. The coating is a blend ofradiation-curable oligomers and monomers, and optionally a free radicalinitiator. The patent discloses that the coating may be applied tocoated or non-coated electronic data processing papers, bond papers,high quality calendared papers, cast coated papers, and other businessforms.

[0011] The ink-jet industry is looking to develop new paper-based mediacapable of absorbing aqueous inks to form high quality images havinggood color density, brilliance, and resolution. The media should havegood moisture-barrier properties and preferably have high surface gloss.A cost-effective and efficient manufacturing process for making suchmedia would also be desirable. The present invention provides suchink-jet recording media and a continuous in-line process formanufacturing the media.

[0012] The ink-jet recording media of this invention comprise aradiation-cured layer and polymeric ink-receptive layer. Theradiation-cured layer helps retain the surface gloss of the media andprovides good moisture barrier properties. Significantly, theradiation-cured layer is thermally stable at temperatures greater thantemperatures at which conventional polyethylene and relatedthermoplastic materials (e.g., olefin-based polymers and copolymers) arethermally stable.

SUMMARY

[0013] The present invention relates to an ink-jet recording mediumcomprising: a) a paper substrate, b) a radiation-cured layer overlayinga surface of the paper substrate, and c) a polymeric ink-receptive layeroverlaying the radiation-cured layer, the ink-jet recording mediumhaving a water vapor transmission rate of no greater than 12 grams per100 square inches per 24 hours (5 g/100 in²/24 hrs). Preferably, thewater vapor transmission rate is no greater than 8 g/100 in²/24 hrs. Themedium preferably has a glossy surface luster. In such glossy mediaembodiments, the surface gloss is at least 70, and it is more preferablyin the range of about 85 to about 95. In other embodiments, satin-likemedia having surface gloss values in the range of 20 to 70 can be made.In still other embodiments, matte-like media having surface gloss valuesless than 20 can be made.

[0014] Preferably, the paper substrate is a clay-coated paper having athickness in the range of about 4 to about 8 mils. The radiation-curedlayer can be formed by irradiating a coating comprising aradiation-curable oligomer and photoinitiator. Preferably, the coatingused to form the radiation-cured layer comprises at least about 60%oligomer and 3% photoinitiator by weight. The coating can furthercomprise radiation-curable monomer and additives. For example, a coatingcomprising 60% oligomer, 3% photoinitiator, 20% monomer, 15% pigment,and 2% UV light stabilizer by weight can be used. Suitable oligomersinclude acrylated polyethers, acrylated polyesters, and acrylatedacrylics. Suitable monomers include trimethylolpropane trimethacrylate.Suitable photoinitiators include 1-hydroxy-cyclohexyl phenyl ketone anda blend of trimethylbenzophenone, polymeric hydroxy ketone, andtrimethylbenzoyldiphenyl phosphine oxide. Generally, the radiation-curedlayer has a weight in the range of about 1 to about 40 grams/squaremeter. Ultraviolet light or electron beam irradiation can be used tocure the coating.

[0015] The ink-receptive layer can comprise a water-soluble binderresin, for example, polyvinyl alcohols, poly(vinyl pyrrolidone),poly(2-ethyl-2-oxazoline), methylcellulose, poly(ethylene oxide), andcopolymers and mixtures thereof. Preferably, the coating comprises atleast 40% water-soluble binder by weight. The coating can furthercomprise a water-dispersible resin. Multiple ink-receptive layers can beapplied to substrate. Generally, the dry coat weight of theink-receptive layer is in the range of about 5 to about 50 grams/squaremeter.

[0016] In another embodiment of this invention, the back surface of thebase paper is coated with a polymeric coating that further helps preventmoisture from penetrating into the base paper. Suitablewater-dispersible resins include, for example, polyvinyl chloride; vinylchloride copolymers; polyvinylidene chloride; vinylidene chloridecopolymers; acrylates; methacrylates; polyvinyl acetate;polyacrylonitrile; polystyrene; styrene copolymers; and mixturesthereof. Alternatively, the polymeric layer on the back surface of thepaper can be a radiation-cured layer formed by irradiating a coatingcontaining radiation-curable oligomers, monomers, photoinitiators andadditives.

[0017] The present invention also relates to a continuous in-lineprocess for making an ink-jet recording medium. In one embodiment, theprocess comprises the steps of a) applying a radiation-curable coatingto a surface of a substrate material, b) irradiating theradiation-curable coating so that the coating undergoes a curingprocess, and c) applying an ink-receptive coating over the irradiatedcoating. Preferably, the media produced by the continuous process have awater vapor transmission rate of no greater than 12 g/100 in²/24 hrs andmore preferably no greater than 5 g/100 in²/24 hrs. Glossy media havinga surface gloss greater than 70 as well as satin-like media having asurface gloss in the range of 20 to 70 and matte-like media having asurface gloss less than 20 can be made. The irradiated coating can betreated with corona discharge prior to applying the ink-receptivecoating. In another embodiment, a coating comprising adhesion promoterscan be applied over the irradiated coating prior to application of theink-receptive coating. As described above, the back surface of thesubstrate material can be coated with a polymeric coating to enhance thematerial's dimensional stability. The continuous in-line process can runat a speed of at least about 60 feet per minute. The irradiated coatinghas good thermal stability. Thus, the substrate comprising theirradiated coating can be subjected to further treatments and processingat temperatures (e.g., 140° C. to 200° C.) greater than temperatures atwhich conventional polyethylene and related thermoplastic materials(e.g., olefin-based polymers and copolymers) are typically treated andprocessed.

BRIEF DESCRIPTION OF THE FIGURE

[0018]FIG. 1 is a schematic side view of one embodiment of the ink-jetrecording medium of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Referring to FIG. 1, the ink-jet recording medium comprises apaper substrate (10) having two surfaces. The first surface which iscoated with the radiation-cured layer and ink-receptive layer may bereferred to as the “front” or “imaging” surface. The second surfacewhich is opposite to the first surface may be coated with the polymericcoating and may be referred to as the “back” or “non-imaging” surface.Paper substrates are known in the ink-jet industry, and any suitablepaper may be used in the present invention. For example, plain papers,clay-coated papers, or resin-coated papers may be used. Preferably, thepaper is a clay-coated paper. Suitable paper substrates include, forexample, Centura Cover 60# paper (available from Consolidated Papers,Inc.) and Polyjet Base 112# paper (available from P.H. GlatfelterCompany). The base weight of the paper is not particularly restricted,but it should be generally in the range of about 80 grams per squaremeter (gsm) to about 250 gsm, preferably in the range of 130 gsm to 180gsm. The thickness of the paper is not particularly restricted, but itshould be generally in the range of about 4 mils to about 8 mils. Thepaper substrate may be pre-treated with conventional adhesion promotersto enhance adhesion of the coatings to the paper or other primercoating.

[0020] As shown in FIG. 1, a radiation-cured layer (12) overlays thefront surface of the base paper. The radiation-cured layer is preparedby first applying a radiation-curable coating to the paper substrate.The coating comprises radiation-curable oligomers and monomers such asacrylated oligomers, multifunctional acrylate monomers, difunctional andmonofunctional monomers, and mixtures thereof. Radiation from anelectron beam or ultraviolet (UV) light source is used to cure the wetcoating. The radiation induces the formation of free radicals thatinitiate polymerization of the oligomers and monomers. In electron beamradiation, a barrage of electrons initiates the free radicalpolymerization. In ultraviolet (UV) light radiation, photoinitiators(photosensitizers) absorb the UV light and initiate the free radicalpolymerization.

[0021] Generally, the radiation-curable oligomers and monomers arecommercially available. For example, acrylated oligomers such asacrylated polyethers, acrylated polyesters, and acrylated acrylics maybe used. It is preferred that a relatively hydrophobic oligomer be usedin the radiation-curable coating. Such a compound helps provide theradiation-cured layer with good moisture barrier properties because asthe hydrophobicity of the oligomer increases, the moisture barrierproperties improve. As a result, moisture is less likely to permeateinto the base paper and paper cockling and curl are minimized. Suitableacrylated oligomers that are commercially available include LAROMER PE44F (acrylated polyester) and LAROMER 8981 (acrylated polyester)available from BASF Corp.; EBECRYL 588 (chlorinated acrylated polyester)available from UCB Chemicals Corp.; and CN 301 (polybutadienedimethacrylate) and CN 302 (polybutadiene diacrylate) available fromSartomer Co. Preferably, the radiation-curable coating comprises anoligomer in an amount of at least about 60% based on weight of thecoating formulation. More preferably, the coating comprises aradiation-curable oligomer selected from the group consisting ofacrylated polyesters, polybutadiene dimethacrylate, and polybutadienediacrylate.

[0022] Suitable radiation-curable monomers include multifunctionalacrylates such as pentaerythritol triacrylate (PETA), trimethylolpropanetriacrylate (TMPTA), 1,6 hexanediol diacrylate (HODA), tritripropyleneglycol diacrylate (TRPGDA), and triethylene glycol diacrylate (TREGDA).Examples of monomers that are commercially available include TMPTA-N(trimethylolpropane triacrylate) and EB-40 (tetraacrylate monomer)available from UCB Chemicals Corp. Difunctional and monofunctionalmonomers also may be used. Examples of monofunctional monomers include2-ethylhexyl acrylate, vinyl acetate, butyl acrylate, dimethylaminoethylacrylate, isobutoxymethyl acrylamide, and dimethylacrylamide.Preferably, the radiation-curable coating comprises a monomer in anamount of about 20% based on weight of the coating formulation. Morepreferably, the radiation-curable monomer is trimethylolpropanetriacrylate (TMPTA).

[0023] In the present invention, UV light radiation is preferably usedto cure the coating, and the coating formulation comprises aphotoinitiator. As discussed above, in UV light radiation,photoinitiators in the coating absorb the UV light and initiate freeradical polymerization. Examples of suitable photoinitiators includeBenzoin ethers (Norrish type I initiator) and Benzophenone (Norrish typeII initiators that require amine coinitiators to be active). IGRACURE184 (1-hydroxy-cyclohexyl phenyl ketone) and phenylbis (2,4,6-trimethylbenzoyl)-phosphine oxide are available from Ciba Specialty ChemicalsCorp., and ESACURE KTO-46 (blend of trimethylbenzophenone, polymerichydroxy ketone, and trimethylbenzoyldiphenyl phosphine oxide) isavailable from Sartomer Co. Preferably, the radiation-curable coatingcomprises a photoinitiator in an amount of at least about 3% based onweight of the coating formulation. More preferably, the coatingcomprises a photoinitiator selected from the group consisting of1-hydroxy-cyclohexyl phenyl ketone and a blend of trimethylbenzophenone,polymeric hydroxy ketone, and trimethylbenzoyldiphenyl phosphine oxide.

[0024] For purposes of the present invention, it is important that theink-jet recording media have a water vapor transmission rate of nogreater than 12.0 grams/100 square inches/24 hours as measured per theTest Methods described below. Preferably, the water vapor transmissionrate is no greater than 5.0 g/100 in²/24hrs. With such media, theink-receptive layer can absorb aqueous-based inks, and the inks tend notto permeate into the base paper. Thus, paper curling, cockling, andother printing defects can be minimized. It has been found that not allradiation-curable compositions are suitable for use in this invention.As shown in the following comparative examples, some radiation-curablecoatings do not impart sufficient moisture barrier properties to themedium.

[0025] The thermal stability of the radiation-cured layer is also animportant property. As discussed above, the substrate comprising theirradiated coating can be subjected to further treatments and processingat temperatures (e.g., 140° C. to 200° C.) greater than temperatures atwhich conventional polyethylene and related thermoplastic materials(e.g., olefin-based polymers and copolymers) are thermally table.Ink-receptive inter- coats and topcoats can be applied to theradiation-cured layer, and these coatings can be subsequently processedwithout distorting or damaging the radiation-cured layer. The thermalstability of the radiation-cured can provide significant processingadvantages.

[0026] For example, the thermal stability of the radiation-cured layercan permit fast or more complete drying of subsequent coating layers.Second, this thermal stability can provide for important chemicalreactions to occur during processing of the media, e.g. a useful degreeof cross-linking in the ink-receptive layer. Cross-linking in theink-receptive layer may be important in achieving good water fastness asdemonstrated in the Examples below. Third, this thermal stability canallow subsequent coating layers to be physically manipulated withrespect to each other and external objects. In particular, the thermalstability of the radiation-cured layer makes it possible to melt thecoating layers to achieve interlayer adhesion, external object adhesione.g., with a laminating film, or a desired surface texture in differentregions of the medium.

[0027] In addition, the radiation-curable coating may comprise additivessuch as, for example, inhibitors, surfactants, waxes, cure accelerators,defoaming agents, pigments, dispersing agents, optical brighteners, UVlight stabilizers (blockers), UV absorbers, adhesion promoters, and thelike. Inhibitors are used to retard or stop undesirable polymerizationof the oligomers and monomers. The addition of such inhibitors to thecoating formulation may be beneficial if the formulation will be placedin storage for an extended period of time. If desired, white pigmentsmay be added to modify the whiteness of the paper. Preferably, theradiation-curable coating comprises pigment in an amount of about 15% byweight and an UV light stabilizer in an amount of about 2% based onweight of the coating formulation.

[0028] In practice, the radiation-curable oligomers and monomers areblended together with a photoinitiator and additives. The mixture may beheated to reduce its viscosity. The coating formulation may be appliedto the base paper by a conventional method to form a uniform coating.Suitable methods for coating the base paper include, for example,Meyer-rod, roller, blade, wire bar, dip, solution extrusion, air-knife,curtain, slide, doctor-knife, and gravure methods. UV light may be usedto cure the wet coating. Generally, the UV light has a wavelength in therange of about 200 nm to about 400 nm. Commercial UV light curingequipment may be used. Generally, such equipment includes an UV lightsource (e.g., a tubular glass lamp), reflectors to focus or diffuse theUV light, and a cooling system to remove heat from the lamp area. Aftercuring, the paper may be treated with corona discharge to improve itsadhesion to the ink-receptive layer. Generally, the weight of theradiation-cured layer is in the range of about 1 to about 40 grams persquare meter (gsm), and the preferable weight is about 4 to about 15gsm.

[0029] The paper substrate is coated with a polymeric ink-receptivelayer (14) that overlays the radiation-cured layer. The ink-receptivelayer is capable of absorbing aqueous-based inks to form glossy imageshaving good color gamut and optical density.

[0030] The polymeric ink-receptive layer can be prepared from a coatingformulation comprising at least one water-soluble binder resin. Suitablewater-soluble binder resins include, for example, those selected fromthe group consisting of polyvinyl alcohols; modified polyvinyl alcohols(e.g., carboxyl-modified PVA, sulfonic-modified PVA, acrylamide-modifiedPVA, cationic-modified PVA, long chain alkyl-modified-PVA,silicone-modified PVA, maleic acid-modified PVA, and itaconicacid-modified PVA); poly(vinyl pyrrolidone); vinyl pyrrolidonecopolymers; poly(2-ethyl-2-oxazoline); poly(ethylene oxide);poly(ethylene glycol); poly(acrylic acids); starch; modified starch(e.g., oxidized starch, cationic starch, hydroxypropyl starch, andhydroxyethyl starch), cellulose; cellulose derivatives (e.g., oxidizedcellulose, cellulose ethers, cellulose esters, methyl cellulose,hydroxyethyl cellulose, carboxymethyl-cellulose, benzyl cellulose,phenyl cellulose, hydroxypropyl cellulose, ethyl hydroxyethyl cellulose,hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxybutylmethyl cellulose, dihydroxypropyl cellulose, hydroxypropylhydroxyethyl cellulose, chlorodeoxycellulose, aminodeoxycellulose,diethylammonium chloride hydroxyethyl cellulose, hydroxypropyl trimethylammonium chloride hydroxyethyl cellulose, sodium cellulose sulfate, andsodium carboxymethylhydroxyethyl cellulose); alginates and water-solublegums; dextrans; carrageenan; xanthan; chitin; proteins; gelatins; agar;and mixtures thereof.

[0031] Preferably, the ink-receptive layer comprises at least onewater-soluble binder resin in an amount of at least 40% and morepreferably in an amount of 45 to 96% by weight based on dry weight ofthe ink-receptive layer. More preferably, the water-soluble binder resinis selected from the group consisting of polyvinyl alcohols; poly(vinylpyrrolidone); poly(2-ethyl-2-oxazoline); methylcellulose; poly(ethyleneoxide); and copolymers and mixtures thereof.

[0032] In addition, the ink-receptive coating formulation may alsocontain a water-dispersible resin. Suitable water-dispersible resinsinclude, for example, those selected from the group consisting ofpolyvinyl chloride; vinyl chloride copolymers (e.g., ethylene-vinylchloride); polyvinylidene chloride; vinylidene chloride copolymers;acrylates; methacrylates; polyvinyl acetate; vinyl acetate copolymers(e.g., ethylene-vinyl acetate copolymers, and acrylic-vinyl acetatecopolymers,) polyacrylonitrile; polystyrene; styrene copolymers (e.g.,styrene-maleic acid anhydride copolymers and styrene-butadienecopolymers); rubber latex; polyesters; vinyl-acrylic terpolymers,polyacrylonitrile; acrylonitrile copolymers (e.g.,butadiene-acrylonitrile copolymers, butadiene-acrylonitrile-styreneterpolymers); polyurethanes; and mixtures thereof.

[0033] In accordance with the present invention, ink-jet recording mediahaving different surface finishes can be made. Preferably, the mediumhas a high surface gloss (greater than 70), and more preferably thesurface gloss is in the range of about 85 to about 95. Such media arecapable of absorbing aqueous-based inks to form glossy images havinggood color gamut and optical density. Conventional ink-jet printers,e.g., an Encad Novajet Pro50, Océ Printing Systems' Océ CS 5070,Hewlett-Packard HP 2500 or HP970 Cse can be used to print such images.The imaged ink-jet recording media can be used to make laminates bylaminating a transparent film over the printed image. Both coldlaminates (i.e., films that are laminated at room temperature), and hotlaminates (i.e., films that are laminated at elevated temperatures) canbe produced.

[0034] In other embodiments, satin-like media having surface glossvalues in the range of 20 to 70 may be made. In still other embodiments,matte-like media having surface gloss values less than 20, e.g., in therange of 1 to 20, may be made.

[0035] Primarily, the ink-receptive layer imparts surface luster to themedia, but the radiation-cured layer is also significant, because ithelps retain surface luster.

[0036] The ink-receptive coating may also contain cationically-modifiedpolymers that act as dye fixatives, e.g., polyquaternary ammonium salts.Further, the ink-receptive coating may contain additives such aspigments. White pigments such as titanium dioxide, zirconium oxide, zincoxide, zinc sulfide, antimony oxide, barium sulfate, and calciumcarbonate may be added to modify the whiteness of the paper. Otherpigments, such as silica, alumina, alumina hydrate, clays, glass,polystyrene, starch, poly(methyl methacrylate), polytetrafluoroethylene,and the like may be added to improve the coating's ink absorptioncapabilities and modify its surface friction. In addition, surfaceactive agents that control the wetting or spreading action of thecoating, anti-static agents, suspending agents, acidic compounds tocontrol the pH of the coating, optical brighteners, UV lightstabilizers, defoaming agents, waxes, plasticizers, and the like may beadded to the formulation.

[0037] In the present invention, the paper substrate may be coated withmultiple ink-receptive layers. For example, a coating formulation (i.e.,inter-coat or prime coat) comprising water, poly(vinyl pyrrolidone),poly(vinyl alcohol), polyurethane, and an optical brightener may beapplied over the radiation-cured layer to form a first ink-receptivelayer. After the inter-coat has been dried, a second coating formulation(i.e., top coat) comprising water, methyl cellulose, polyethylene oxide,polyurethane, and alumina may be applied over the first ink-receptivelayer to form a second ink-receptive layer.

[0038] Further, the media may comprise an intermediate coating layer(s)between the radiation-cured and ink-receptive coating layers. Forexample, a coating comprising adhesion promoters may be applied over theradiation-cured layer to enhance adhesion of the radiation-cured layerto the ink-receptive layer.

[0039] In practice, a water-soluble binder resin may be blended withwater, and a water-dispersible binder resin (optional) and additives(optional) to form a coating formulation. A pre-mix containing a portionof the water-soluble resins may be prepared first in a small vessel andthen added to a larger vessel. Subsequently, additives and other resinsmay be added and mixed together in the larger vessel. Various coatingmethods may be used to apply the ink-receptive coating to the substrateincluding Meyer-rod, roller, blade, wire bar, dip, solution extrusion,air-knife, curtain, slide, doctor-knife, and gravure methods. Thecoating formulations should have a low and consistent viscosity so thatthey can be coated easily onto the radiation-cure layer. The coatedpaper may be placed in a forced hot air oven to dry the ink-receptivelayer. Generally, the dry coat weight of the ink-receptive layer is inthe range of about 5 to about 50 gsm, and the preferable weight is about15 to about 25 gsm.

[0040] In addition, the back surface of the base paper may be coated apolymeric coating (16) that further helps prevent moisture frompenetrating into the base paper. The polymeric coating on the backsurface of the paper enhances the paper's dimensional stability andhelps minimize paper curling, cockling, and other defects.

[0041] In one embodiment, a polymeric coating (16) comprising awater-dispersible film-forming resin may be prepared. Suitablewater-dispersible resins include, for example, polyvinyl chloride; vinylchloride copolymers (e.g., ethylene-vinyl chloride); polyvinylidenechloride; vinylidene chloride copolymers; vinyl acrylic copolymers,vinyl acrylic terpolymers, polyacrylates; polymethacrylates; polyvinylacetate; polyacrylonitrile; polystyrene; styrene butadiene copolymers,styrene copolymers; and mixtures thereof. An aqueous coating formulationcontaining the film-forming resin may be prepared and applied to theback surface of the base paper using the coating methods describedabove. The polymeric coating may contain the above-described additivesparticularly waxes and pigments. In other embodiments, the polymericlayer on the back surface of the paper is a radiation-cured layerprepared from a coating containing radiation-curable oligomers,monomers, photoinitiators and additives as described above. If apolymeric coating is applied to the back surface, the dry coat weight ofthe polymeric layer is generally in the range of about 5 to about 40gsm, and the preferable weight is about 15 to about 25 gsm.

[0042] The present invention also encompasses a continuous, in-lineprocess for making an ink-jet recording medium. In general, the processcomprises the steps of: a) applying a radiation-curable coating to asurface of a substrate material, b) irradiating the radiation-curablecoating so that the coating undergoes a curing process, and c) applyingan ink-receptive coating over the irradiated coating.

[0043] While not wishing to be bound by any theory, it is believed thatthe continuous, in-line process of this invention may provide advantagesover other production methods. As discussed above, the substrate iscoated with a radiation-curable composition, and the coating isirradiated soon thereafter. The irradiated coating undergoes a curingprocess comprising multiple constituent chemical and physical processes.The constituent irradiation and curing processes include the formationof active sites by irradiation (typically free radicals), the reactionor deactivation of these sites (typically through cross-linking orquenching with adventitious oxygen), the thermally and mechanicallyinduced relaxation of the coating morphology to more stableconfigurations (typically the molecular relaxation to configurationsthat are more stable under the circumstances), drying, and similarprocesses.

[0044] It is believed that the irradiated coating, as it undergoes thecuring process, will respond to post in-line treatments differently thaneither a fully cured or a non-irradiated coating (e.g., theabove-described polyethylene-coated papers). The “freshly irradiated”coating will have surface properties that are different than those of asubstrate having a fully cured or a non-irradiated coating. Thesedifferences can be exploited to make subsequently applied coating layersadhere either strongly or weakly to the freshly irradiated coating.Further, the surface properties of the “freshly irradiated coating” canbe exploited to increase production efficiency, reduce powerconsumption, or alter the composition of subsequently applied coatinglayers. For example, the freshly irradiated coating can becorona-treated as the substrate travels along the production line. If acoating layer must be subjected to corona treatment for a specificperiod of time in order to produce a layer having acceptable surfaceproperties, it is possible that the same properties could be imparted toa “freshly irradiated” coating in less time using the same coronatreatment. As a result, the production line could be run at higherspeeds, or power delivered to the corona discharge unit could bereduced, or space requirements for the corona treatment station could bereduced.

[0045] The in-line irradiation of the radiation-curable coating canprovide additional advantages. An important advantage relates tochemical interactions between the “freshly irradiated” coating and posttreatments. Some of the most reactive chemical units present uponirradiation, such as free radicals, are not present to a useful degreein a fully cured coating. A coating designer can employ a “freshlyirradiated” coating to impart desirable properties to the ink-jetrecording media. Also, the physical, or material, properties of a“freshly irradiated” coating and a fully cured coating are different.Typically, the “freshly irradiated” coating is softer and more compliantthan a fully cured one. As a result, the freshly irradiated coating canbe processed advantageously using physical adhesion, pattern impression,and similar processes. Further, since the “freshly irradiated” coatingis not filly cured, molecular motion and transport into and out of thecoating tends to be easier. This molecular motion and transport mayallow for interfacial blending with other coating layers, and this canbe advantageous in improving adhesion, controlling curl of the media,and responding to other external environmental factors such as changesin humidity.

[0046] It may be advantageous to treat the irradiated coating within one(1) minute of irradiation. In such a process, the irradiation stationand next treatment station (e.g., a corona discharge unit) in theproduction line would be within sixty (60) feet of each other. Thesubstrate would travel at a speed of at least sixty (60) feet per minuteas it progressed along the production line.

[0047] The invention is further illustrated by the following examplesusing the below Test Methods, but these examples should not be construedas limiting the scope of the invention.

Test Methods Water Vapor Transmission (WVT)

[0048] The water vapor transmission (WVT) rate of the samples wasmeasured using a Vapometer (available from Thwing-Albert InstrumentCompany) according to the standard procedures described in theinstrument manual provided by the manufacturer. Particularly, thesamples were equilibrated at 15° C. and 20% relative humidity for about24 hours. The water vapor transmission (WVT) was then measured on aVapometer at 15° C. and 20% relative humidity for 24 hours. Measurementswere made on three (3) samples, and the average value was reported.

Surface Gloss

[0049] The surface gloss of the samples was measured using a MicroTri-Gloss Meter (available from BYK Gardner, Inc.) according to thestandard procedures described in the instrument manual provided by themanufacturer. Particularly, the sample was cut into sheets measuring 8.5inch by 11 inch. The surface gloss was measured on the sheets prior toimaging (printing). The Micro-Tri Gloss Meter was calibrated at sixty(60) degrees using the standard supplied by the unit. The sample wasplaced on a flat surface and the surface gloss was measured at sixty(60) degrees. Measurements were made on three (3) samples, and theaverage value was reported.

Color Gamut

[0050] The media samples were imaged (printed) with an Encad NovajetPro50 printer containing GS ink using an IAS2 test pattern. The printedsamples were stored at room temperature for 24 hours. Subsequently, thecolor gamut of each sample was measured with a X-RITE 918 TristimulusReflection Colorimeter (available from X-Rite, Inc.) using standardprocedures described in the instrument manual provided by themanufacturer. Generally, media having higher color gamut values provideimages of higher color quality.

Optical Density

[0051] The media samples were imaged (printed) with a multicolored testpattern using an Encad Novajet Pro50 printer containing GS ink. Theprinted samples were stored at room temperature for 24 hours.Subsequently, the optical density of black ink for each sample wasmeasured with a X-Rite 408 Reflection Densitometer (available fromX-Rite, Inc.) using standard procedures described in the instrumentmanual provided by the manufacturer. Generally, media having higheroptical density values provide images of higher quality and resolution.

Thermal Stability

[0052] The thermal stability of the radiation-cured layer on papersubstrate samples was tested. The test was carried out at settemperatures in the range of 150° C. to 200° C., but it can be carriedout at any desired temperature. The paper substrate samples were coatedwith a radiation-curable coating, and the coating was irradiated asdescribed in the Examples below. The irradiated, coated surface of thepaper substrate was placed in contact with a heated plate for one (1)minute. Then, the coated surface of the paper was visually inspected todetermine whether or not there was any damage or changes to the surface.Such changes could be a chemical change or a significant physical changesuch as melting or other structural modification. If no surface damageor change was observed, then the coated surface was rated as a “Pass”for that test temperature. If surface damage or change was observed,then the coated surface was rated as a “Fail” for that test temperature.

Water-Fastness

[0053] The media samples were imaged (printed) using a small formatink-jet printer, Hewlett-Packard 970 Cxi. The printed samples werestored at room temperature for 24 hours. The density of each of thecolored print areas on each sample was measured with a X-Rite 408Reflection Densitometer (available from X-Rite, Inc.) using standardprocedures described in the instrument manual provided by themanufacturer.

[0054] The printed samples were then immersed in water for 12 hours. Thewet, printed samples were removed and dried at room temperature for 12hours. Then, the density of each of the colored print areas on eachsample was measured with an X-Rite 408 Reflection Densitometer. The losspercentage (%) of color was calculated according to the followingequation:${\frac{\left( {{Initial}\quad {Density}} \right) - \left( {{Final}\quad {Density}} \right)}{\left( {{Initial}\quad {Density}} \right)} \times 100} = {{loss}\quad \% \quad {of}\quad {color}}$

[0055] Generally, media having a relatively high percentage of colorloss possess poor water-fastness, and media having a relatively lowpercentage of color loss possess good water-fastness.

WORKING EXAMPLES

[0056] In the following examples, percentages are by weight based onweight of the coating formulation, unless otherwise indicated. Theresulting ink-jet recording media samples were evaluated, and theresults are set forth in Tables 1 and 2 below.

EXAMPLE 1

[0057] The following coating formulations were prepared. UV LightRadiation-Curable Coating Laromer PE 44F¹ 95 wt. % Irgacure 184² 5 wt. %Ink-Receptive Coating (Intercoat) Water 70.5 wt. % PVA KM 118³ 4 wt. %PVP K-60⁴ 16 wt. % Witcobond 213⁵ 9 wt. % BYK-380⁶ 0.5 wt. %Ink-Receptive Coating (Topcoat) Water 90.6 wt. % PVA KM 118 4 wt. % PVPK-60 5 wt. % BYK-380 0.3 wt. % Citric Acid 0.1 wt. % Polymeric Coatingfor Back Surface (Aqueous) Vancryl 610⁷ 93.7 wt. % Lanco PEW 1555⁸ 5 wt.% Surfynol SE-F⁹ 1.0 wt. % Surfynol CT 171¹⁰ 0.2 wt. % DREW Plus L-407¹¹0.1 wt. %

[0058] The radiation-curable coating was applied to the front surface ofa 5.5 mil clay-coated paper substrate (Centura Cover 60# paper availablefrom Consolidated Papers Inc.) using an offset gravure coater with agravure roll (85 pyramid roll). The wet coating was cured by a Fusion UVlight curing system (Model VP6/I600) (available from Fusion UV Systems,Inc., Gaithersburg, Md. 20878) with two rows of 300 watts/cm H-bulbs.The UV lamp power intensity was set at 100%. After UV curing, theradiation-cured layer was subjected to corona discharge treatment.

[0059] After corona discharge treatment, the first ink-receptive coating(intercoat) was applied over the radiation-cured layer using a Meyerrod, and the coating was dried at 225° F. The first ink-receptive layercomprised 28% polyvinyl alcohol, 51% polyvinyl pyrrolidone, 19%polyurethane, and 2% acrylic leveling agent by weight based on dryweight of the ink-receptive layer. The second ink-receptive coating(topcoat) was applied over the intercoat using a Meyer rod and dried at225° F. The second ink-receptive layer comprised 62% polyvinyl alcohol,34% polyvinyl pyrrolidone, 2.4% acrylic leveling agent, and 2.5% citricacid by weight based on dry weight of the ink-receptive layer.

[0060] The polymeric coating was applied to the back surface of thepaper using a Meyer rod, and the coating was dried at 220° F. Thepolymeric coating comprised about 88% ethylene-vinyl chloride copolymer,9% low molecular weight polyethylene wax, 2.8% diol surfactants, and0.2% modified polysiloxane copolymer by weight based on dry weight ofthe polymeric coating.

EXAMPLE 2

[0061] The following coating formulations were prepared. UV LightRadiation-Curable Coating Laromer PE 44F 75 wt. % TMPTA-N¹ 20 wt. %Irgacure 184 5 wt. % Ink-Receptive Coating (Intercoat) Same compositionas described in Example 1. Ink-Receptive Coating (Topcoat) Samecomposition as described in Example 1. Polymeric Coating for BackSurface (Aqueous) Same composition as described in Example 1.

[0062] In this Example 2, the radiation-curable coating contained aradiation-curable monomer (TMPTA-N) along with an oligomer andphotoinitiator. The ink-receptive and moisture-barrier coatings had thesame compositions as described in Example 1. The radiation-curable,ink-receptive, and polymeric coatings were applied to a 5.5 milclay-coated paper (Centura Cover 60# paper) and treated in the samemanner as described in Example 1.

EXAMPLE 3

[0063] The following coating formulations were prepared. UV LightRadiation-Curable Coating Laromer PE 44F 38 wt. % Ebecryl 588¹ 38 wt. %TMPTA-N 20 wt. % Irgacure 184 4 wt. % Ink-Receptive Coating (Intercoat)Same composition as described in Example 1. Ink-Receptive Coating(Topcoat) Same composition as described in Example 1. Polymeric Coatingfor Back Surface (Aqueous) Same composition as described in Example 1.

[0064] In this Example 3, the radiation-curable coating contained tworadiation-curable oligomers (Laromer PE 44F and Ebecryl 588), a monomerand photoinitiator. The ink-receptive and moisture-barrier coatings hadthe same compositions as described in Example 1. The radiation-curable,ink-receptive, and polymeric coatings were applied to a 5.5 milclay-coated paper (Centura Cover 60# paper) and treated in the samemanner as described in Example 1.

EXAMPLE 4

[0065] The following coating formulations were prepared. UV LightRadiation-Curable Coating Laromer PE 44F 38 wt. % CN 301¹ 38 wt. %TMPTA-N 20 wt. % Irgacure 184 4 wt. % Ink-Receptive Coating (Intercoat)Same composition as described in Example 1. Ink-Receptive Coating(Topcoat) Same composition as described in Example 1. Polymeric Coatingfor Back Surface (Aqueous) Same composition as described in Example 1.

[0066] In this Example 4, the radiation-curable coating contained tworadiation-curable oligomers (Laromer PE 44F and CN 301) along with amonomer and photoinitiator. The ink-receptive and polymeric coatings hadthe same compositions as described in Example 1. The radiation-curable,ink-receptive, and polymeric coatings were applied to a 5.5 milclay-coated paper (Centura Cover 60# paper) and treated in the samemanner as described in Example 1.

EXAMPLE 5

[0067] The following coating formulations were prepared. UV LightRadiation-Curable Coating Laromer PE 44F 38 wt. % CN 302¹ 38 wt. %TMPTA-N 20 wt. % Irgacure 184 4 wt. % Ink-Receptive Coating (Intercoat)Same composition as described in Example 1. Ink-Receptive Coating(Topcoat) Same composition as described in Example 1. Polymeric Coatingfor Back Surface (Aqueous) Same composition as described in Example 1.

[0068] In this Example 5, the radiation-curable coating contained tworadiation-curable oligomers (Laromer PE 44F and CN 302) along with amonomer and photoinitiator. The ink-receptive and polymeric coatings hadthe same compositions as described in Example 1. The radiation-curable,ink-receptive, and polymeric coatings were applied to a 5.5 milclay-coated paper (Centura Cover 60# paper) and treated in the samemanner as described in Example 1.

EXAMPLE 6

[0069] The following coating formulations were prepared. UV LightRadiation-Curable Coating Ebecryl 588 40 wt. % CN 301 40 wt. % TMPTA-N15 wt. % Irgacure 184 5 wt. % Ink-Receptive Coating (Intercoat) Samecomposition as described in Example 1. Ink-Receptive Coating (Topcoat)Same composition as described in Example 1. Polymeric Coating for backSurface (Aqueous) Same composition as described in Example 1.

[0070] In this Example 6, the radiation-curable coating contained tworadiation-curable oligomers (Ebecryl 588 and CN 301) along with amonomer and photoinitiator. The ink-receptive and polymeric coatings hadthe same compositions as described in Example 1. The radiation-curable,ink-receptive, and polymeric coatings were applied to a 5.5 milclay-coated paper (Centura Cover 60# paper) and treated in the samemanner as described in Example 1.

EXAMPLE 7

[0071] The following coating formulations were prepared. UV LightRadiation-Curable Coating Laromer PE 44F 20 wt. % Ebecryl 588 38 wt. %CN 301 20 wt. % TMPTA-N 17 wt. % Irgacure 184 5 wt. % Ink-ReceptiveCoating (Intercoat) Same composition as described in Example 1.Ink-Receptive Coating (Topcoat) Same composition as described inExample 1. Polymeric Coating for Back Surface (Aqueous) Same compositionas described in Example 1.

[0072] In this Example 7, the radiation-curable coating contained threeradiation-curable oligomers (Laromer PE 44F, Ebecryl 588, and CN 301)along with a monomer and photoinitiator. The ink-receptive and polymericcoatings had the same compositions as described in Example 1. Theradiation-curable, ink-receptive, and polymeric coatings were applied toa 5.5 mil clay-coated paper (Centura Cover 60# paper) and treated in thesame manner as described in Example 1.

EXAMPLE 8

[0073] The following coating formulations were prepared. UV LightRadiation-Curable Coating Laromer PE 44F 20 wt. % Ebecryl 588 20 wt. %CN 302 38 wt. % TMPTA-N 17 wt. % Irgacure 184 5 wt. % Ink-ReceptiveCoating (Intercoat) Same composition as described in Example 1.Ink-Receptive Coating (Topcoat) Same composition as described inExample 1. Polymeric Coating for Back Surface (Aqueous) Same compositionas described in Example 1

[0074] In this Example 8, the radiation-curable coating contained threeradiation-curable oligomers (Laromer PE 44F, Ebecryl 588, and CN 302)along with a monomer and photoinitiator. The ink-receptive and polymericcoatings had the same compositions as described in Example 1. Theradiation-curable, ink-receptive, and polymeric coatings were applied toa 5.5 mil clay-coated paper (Centura Cover 60# paper) and treated in thesame manner as described in Example 1.

EXAMPLE 9

[0075] The following coating formulations were prepared. UV LightRadiation-Curable Coating Laromer PE 44F 59 wt. % TMPTA-N 20 wt. %Kronos 1072¹ 15 wt. % Esacure KTO-46² 3 wt. % Irgacure 184 1 wt. %Tinuvin 292³ 2 wt. % Ink-Receptive Coating (Intercoat) Water 73.5 wt. %Airvol 523S⁴ 4 wt. % PVP K-60 11 wt. % Sancure 815⁵ 11 wt. % BYK-380 0.5wt. % Ink-Receptive Coating (Topcoat) Water 65.6 wt. % Methocel E-15LV⁶5 wt. % Methocel K-3⁷ 1 wt. % PolyOX N80⁸ 1 wt. % Witcobond W-213 4 wt.% Dispal 23N4-20⁹ 23 wt. % BYK-380 0.4 wt. % Polymeric Coating for BackSurface (Aqueous) Rhoplex B-88¹⁰ 44.3 wt. % Haloflex 202-S¹¹ 44.3 wt. %Surfynol SE-F 0.9 wt. % Surfynol CT 171 0.2 wt. % DREW PLUS L-407 0.3wt. % Lanco PEW 1555 10 wt. %

[0076] In this Example 9, the radiation-curable coating containedradiation-curable monomer (TMPTA-N) along with an oligomer (Laromer PE44F), titanium oxide pigment (Kronos 1072), two photoinitiators (EsacureKTO-46, Irgacure 184), dispersant agent, and light stabilizer (Tinuvin292). The radiation-curable coating was applied to a 5.5 mil clay-coatedpaper (Centura Cover 60# paper) and treated in the same manner asdescribed in Example 1.

[0077] The first ink-receptive coating (intercoat) was applied over theradiation-cured layer using a Meyer rod, and the coating was dried at225° F. The first ink-receptive layer comprised about 31% polyvinylalcohol, 38% polyvinyl pyrrolidone, 29% polyurethane, and 2% acrylicleveling agent by weight based on dry weight of the ink-receptive layer.The second ink-receptive coating (topcoat) was applied over theintercoat using a Meyer rod and dried at 225° F. The secondink-receptive layer comprised about 42% hydroxypropyl methylcellulose,7% polyethylene oxide, 8.5% polyurethane, 41% aluminum oxide, and 1.5%acrylic leveling agent by weight based on dry weight of theink-receptive layer.

[0078] The aqueous polymeric coating was applied to the backside of thepaper using a Meyer rod, and the coating was dried at 220° F. Thepolymeric layer comprised about 33% acrylic polymer, 47% vinyl acrylicterpolymer, 18% low molecular weight polyethylene wax, 1.5% diol, and0.5% modified polysiloxane copolymer by weight based on dry weight ofthe polymeric layer.

EXAMPLE 10

[0079] The following coating formulations were prepared. UV LightRadiation-Curable Coating Same composition as described in Example 3.Ink-Receptive Coating (Intercoat) Same composition as described inExample 9. Ink-Receptive Coating (Topcoat) Same composition as describedin Example 9. Polymeric Coating for Back Surface (UV lightradiation-curable) Laromer PO 43F¹ 85 wt. % Gasil UV 70C² 10 wt. %Irgacure 184 5 wt. %

[0080] In this Example 10, the UV light-radiation curable coating hadthe same composition as described in Example 3. The ink-receptivecoatings had the same compositions as described in Example 9. Theradiation-curable and ink-receptive coatings were applied to a 5.5 milclay-coated paper (Centura Cover 60# paper) and treated in the samemanner as described in Example 1. The polymeric layer containedradiation-curable oligomer (Laromer PO 43F) and photoinitiator (Irgacure184) along with silica dioxide (Gasil UV 70C).

EXAMPLE 11

[0081] The following coating formulations were prepared. UVLight-Radiation Curable Coating Laromer 8981¹ 59 wt. % TMPTA-N 20 wt. %Ti-Pure R-960² 15 wt. % CGI 819 XF³  1 wt. % Irgacure 184  3 wt. %Tinuvin 292  2 wt. % Ink-Receptive Coating Water 75.8 wt. % GelitaT-7838⁴ 11 wt. % Syntran HX31-65⁵ 13 wt. % Heloxy Modifier 48⁶  0.2 wt.% Polymeric Coating for Back Surface (Aqueous) Same composition asdescribed in Example 9.

[0082] In this Example 11, the radiation-curable coating containedradiation-curable monomer (TMPTA-N) along with an oligomer (Laromer8981), titanium dioxide pigment (Ti-Pure R-960), two photoinitiators(CGI 819 XF, Irgacure 184), dispersant agent, and light stabilizer(Tinuvin 292). The radiation-curable coating was applied to a 5.5 milclay-coated paper (Centura Cover 60# paper) and treated in the samemanner as described in Example 1.

[0083] The ink-receptive coating was applied over the radiation-curedlayer using a Meyer rod, and the coating was dried at 302° F. for 2minutes. The ink-receptive layer comprised about 70% water-solublegelatin, 29% acrylate copolymer, 1% diglycidyl ether of dibromoneopentyl glycol by weight based on dry weight of the ink-receptivelayer.

[0084] The aqueous polymeric coating was applied to the backside of thepaper and treated in the same manner as described in Example 9

EXAMPLE 12

[0085] The following coating formulations were prepared.

UV Light Radiation-Curable Coating

[0086] Same composition as described in Example 3.

Ink-Receptive Coating (Intercoat)

[0087] Same composition as described in Example 1.

Ink-Receptive Coating (Topcoat)

[0088] Same composition as described in Example 1.

Polymeric Coating for Back Surface

[0089] None

[0090] In this Example 12, the radiation-curable coating had the samecomposition as described in Example 3. The ink-receptive coatings hadthe same compositions as described in Example 1. The radiation-curableand ink-receptive coatings were applied to a 5.5 mil clay-coated paper(Centura Cover 60# paper) and treated in the same manner as described inExample 1. No polymeric coating was applied to the back surface of thepaper.

EXAMPLE 13

[0091] The following coating formulations were prepared. UV LightRadiation-Curable Coating Laromer PE 44F 59 wt. % TMPTA-N 20 wt. %Kronos 1072 15 wt. % Esacure KTO-46  3 wt. % Irgacure 184  1 wt. %Tinuvin 292  2 wt. % Ink-Receptive Coating Water 75 wt. % Gelita T-783811 wt. % Syntran HX31-65 13 wt. % Heloxy Modifier 48  0.2 wt. %Polymeric Coating for Back Surface (Aqueous) Rhoplex B-88¹⁰ 44.3 wt. %Haloflex 202-S¹¹ 44.3 wt. % Surfynol SE-F  0.9 wt. % Surfynol CT 171 0.2 wt. % DREW PLUS L-407  0.3 wt. % Lanco PEW 1555 10 wt. %

[0092] The radiation-curable coating was applied to a 5.5 milclay-coated paper (Centura Cover 60# paper) and treated in the samemanner as described in Example 1.

[0093] The ink-receptive coating was applied over the radiation-curedlayer using a Meyer rod, and the coating was dried at 302° F. (150° C.)for 2 minutes. The aqueous polymeric coating was applied to the backsideof the paper and treated in the same manner as described in Example 9.

[0094] The thermal stability of the radiation-cured layer on the papersubstrate was tested per the Test Methods described above. The test wasconducted at set temperatures in the range of 150° C. to 200° C., andthe coated surface was rated a “pass” at each temperature.

EXAMPLE 14

[0095] The following coating formulations were prepared. UV LightRadiation-Curable Coating Same composition as described in Example 2.Ink-Receptive Coating (Intercoat) Same composition as described inExample 1. Ink-Receptive Coating (Topcoat) Water 92.2 wt. % PVA KM118 3.5 wt. % PVP K-60  3 wt. % Syloid 72¹  0.8 wt. % Citric acid  0.1 wt.% BYK-380  0.4 wt. % Polymeric Coating for Back Surface (Aqueous) Samecomposition as described in Example 1.

[0096] In this Example 14, the radiation-curable coating had the samecomposition as described in Example 2. The first ink-receptive layer andpolymeric back coating had the same compositions as described in Example1.

[0097] The second ink-receptive layer comprised 59% polyvinyl alcohol,23% polyvinyl pyrrolidone, 13% silica, 3% acrylic leveling agent, and 2%citric acid by weight based on dry weight of the ink-receptive layer.

[0098] The radiation-curable, ink-receptive, and polymeric back coatingswere applied to a 5.5 mil clay-coated paper (Centura Cover 60# paper)and treated in the same manner as described in Example 1.

EXAMPLE 15

[0099] The following coating formulations were prepared. UV LightRadiation-Curable Coating Same composition as described in Example 2.Ink-Receptive Coating (Intercoat) Same composition as described inExample 1. Ink-Receptive Coating (Topcoat) Water 92.6 wt. % PVA KM118 3wt. % PVP K-60 2 wt. % Syloid 72 2 wt. % Citric acid 0.1 wt. % BYK-3800.3 wt. % Polymeric Coating for Back Surface (Aqueous) Same compositionas described in Example 1.

[0100] In this Example 15, the radiation-curable coating had the samecomposition as described in Example 2. The first ink-receptive layer andmoisture-barrier coatings had the same compositions as described inExample 1.

[0101] The second ink-receptive layer comprised 49% polyvinyl alcohol,15% polyvinyl pyrrolidone, 32.5% silica, 2% acrylic leveling agent, and1.5% citric acid by weight based on dry weight of the ink-receptivelayer.

[0102] The radiation-curable, ink-receptive, and moisture-barriercoatings were applied to a 5.5 mil clay-coated paper (Centura Cover 60#paper) and treated in the same manner as described in Example 1.

EXAMPLE 16

[0103] In this Example 16, a continuous, in line process was used tomanufacture the ink-jet recording medium.

[0104] First, the UV-light radiation-curable coating described inExample 9 was applied to the front surface of a 5.5 mil clay-coatedpaper substrate (Centura Cover 60# paper available from ConsolidatedPapers Inc.) using an offset gravure coater with a gravure roll (85 quadchanneled roll) at a first coating station. The wet coating was cured bya Fusion UV light curing system (Model VP6/I600) (available from FusionUV Systems, Inc., Gaithersburg, Md. 20878) with two rows of 600 watts/cmH+-bulbs. The UV lamp power intensity was set at 100%. The line speedwas greater than 100 feet per minute (fpm). After progressing throughthe UV light curing station, the web passed through a corona treatmentstation, wherein the radiation-cured layer was corona-treated using 2.5kW of corona-treating power. After corona discharge treatment, the webprogressed to a second coating station, where the inter-coatink-receptive coating described in Example 9 was applied over theradiation-cured layer using a Meyer rod. The inter-coat was dried in anin-line dryer at 225° F. Then, the web progressed to a third coatingstation, where the top coat ink-receptive coating described in Example 9was applied over the inter-coat layer using a Meyer rod. The topcoat wasdried in an in-line dryer at 225° F. Then, the running web passed over aturning bar. The back surface of the running web was coated with theaqueous polymeric coating described in Example 9 in a fourth coatingstation. The aqueous back coating was applied using a Meyer rod, and thecoating was dried at 220° F.

Comparative Example A

[0105] The following coating formulations were prepared. UV LightRadiation-Curable Coating Laromer PE 44F 47.75 wt. % Laromer 8765¹ 47.75wt. % Irgacure 184  4.5 wt. % Ink-Receptive Coating (Intercoat) Samecomposition as described in Example 9. Ink-Receptive Coating (Topcoat)Same composition as described in Example 9. Polymeric Coating for BackSurface (Aqueous) Same composition as described in Example 1.

[0106] In this Comparative Example A, the radiation-curable coatingcontained two radiation-curable oligomers (Laromer PE 44F and Laromer8965) and one photoinitiator (Irgacure 184). The ink-receptive coatingshad the same compositions as described in Example 9. Theradiation-curable coating and ink-receptive coatings were applied to a5.5 mil clay-coated paper (Centura Cover 60# paper) and treated in thesame manner as described in Example 1.

Comparative Example B

[0107] The following coating formulations were prepared.

UV Light Radiation-Curable Coating

[0108] None

Ink-Receptive Coating

[0109] Same composition as described in Example 13.

Polymeric Coating for Back Surface

[0110] None (* JEN COAT 6 mil polycoated paper having a polyethylenecoating on both sides of the paper was used.)

[0111] The ink-receptive coating was applied to a JEN COAT 6 milpolycoated white glossy paper (a polyethylene coated paper availablefrom Jen-Coat, Inc. Westfield, Mass.) The ink-receptive coating wasapplied to the surface of the paper using a Meyer rod, and the coatingwas dried at 250° F. (121° C.) for 2 minutes.

[0112] The thermal stability of the radiation-cured layer on the papersubstrate was tested per the Test Methods described above. The test wasconducted at set temperatures in the range of 150° C. to 200 ° C., andthe coated surface was rated a “fail” at each temperature. TABLE 1 ColorWVT Surface Gloss Gamut Color Density Example (g/in²/24 hrs.) (at 60°angle) Value (black color) Example 1 2.0 88 2609 2.58 Example 2 2.0 892615 2.55 Example 3 2.0 89 2605 2.57 Example 4 2.0 88 2610 2.64 Example5 2.0 89 2532 2.47 Example 6 2.0 88 2566 2.57 Example 7 2.0 89 2620 2.63Example 8 2.0 87 2609 2.53 Example 9 1.4 89 2601 2.78 Example 10 4.7 872583 2.78 Example 11 1.4 97 2345 2.78 Example 12 3.8 89 2605 2.57Example 13 1.4 97 2345 2.78 Example 14 2.0 41 2490 2.79 Example 15 2.0 71605 1.87 Example 16 4.8 83 2454 2.45 Comp. Ex. A 14.3 88 2601 2.78

[0113] Referring to Table 1, in Comparative Example A, the UV lightradiation-curable coating contained two radiation-curable polyesteracrylate oligomers and a photoinitiator. The resultant mediumdemonstrated high surface gloss, but its water vapor transmission (WVT)rate was also high (14.3 grams/sq. in/24 hours).

[0114] However, as shown in Examples 1-16, it has been found that mediahaving low water vapor transmission (WVT) rates and different surfacegloss values can be prepared using certain UV light radiation-curable,ink-receptive, and moisture-barrier coatings. Moreover, the media inExamples 1-16 provide ink-jet images having good color gamut and opticaldensity. TABLE 2 (Water Fastness-Loss % of Color) Example Black RedGreen Yellow Blue Magenta Cyan Ex. 13 35% 12%  4%  7%  4% 24%  4% Comp.B 54% 45% 27% 12% 30% 31% 11%

[0115] Referring to Table 2, the ink-jet recording medium of Example 13demonstrated superior water-fastness versus the ink-jet recording mediumof Comparative Example B, although the same water-fast, ink-receptivecoating was applied to each of the substrates at the same coat weights.It is believed that the superior water-fastness of the medium in Example13 is due to it being treated at 302° F. (150° C.) for 2 minutes, whilethe medium in Comparative Example B was treated at 250° F. (121° C.) for2 minutes. As noted above, the JEN-COAT polycoated paper in ComparativeExample B failed the thermal stability test at 150° C.; thus, it had tobe heated at lower temperatures to achieve drying and other thermallyinduced changes. In Example 13, the greater thermal stability of theradiation-cured coating made it possible to process the ink-receptivelayer at higher temperatures and obtain superior water-fastnessproperties.

1. An ink-jet recording medium comprising: a) a paper substrate having asurface, b) a radiation-cured layer overlaying the surface of the papersubstrate, and c) a polymeric ink-receptive layer overlaying theradiation-cured layer, wherein the ink-jet recording medium has a watervapor transmission rate of no greater than 12 grams/100 square inches/24hours and a surface gloss of at least
 70. 2. The ink-jet recordingmedium of claim 1, wherein the paper substrate is a clay-coated paper.3. The ink-jet recording medium of claim 1, wherein the paper substratehas a thickness in the range of about 4 mils to about 8 mils.
 4. Theink-jet recording medium of claim 1, wherein the radiation-cured layeris formed by irradiating a coating comprising a radiation-curableoligomer and a photoinitiator.
 5. The ink-jet recording medium of claim4, wherein the radiation-curable oligomer is selected from the groupconsisting of acrylated polyethers, acrylated polyesters, and acrylatedacrylics.
 6. The ink-jet recording medium of claim 4, wherein thephotoinitiator is selected from the group consisting of1-hydroxy-cyclohexyl phenyl ketone and a blend of trimethylbenzophenone,polymeric hydroxy ketone, and trimethylbenzoyldiphenyl phosphine oxide.7. The ink-jet recording medium of claim 4, wherein the coating furthercomprises a radiation-curable monomer.
 8. The ink-jet recording mediumof claim 7, wherein the radiation-curable monomer is trimethylolpropanetrimethacrylate.
 9. The ink-jet recording medium of claim 4, wherein thecoating further comprises an additive selected from the group consistingof inhibitors, surfactants, waxes, cure accelerators, defoaming agents,pigments, optical brighteners, UV light stabilizers, and mixturesthereof.
 10. The ink-jet recording medium of claim 1, wherein the weightof the radiation-cured layer is in the range of about 1 to about 40grams/square meter.
 11. An ink-jet recording medium comprising: a) apaper substrate having a surface, b) a radiation-cured layer overlayingthe surface of the paper substrate, said layer formed by irradiating acoating comprising at least about 60% radiation-curable oligomer byweight based on weight of the coating, and c) an ink-receptive layeroverlaying the radiation-cured layer, wherein the ink-jet recordingmedium has a water vapor transmission rate of no greater than 12grams/100 square inches/24 hours and a surface gloss of at least
 70. 12.An ink-jet recording medium comprising: a) a paper substrate having asurface, b) a radiation-cured layer overlaying the surface of the papersubstrate, said layer formed by irradiating a coating comprising about60% radiation-curable oligomer, 20% radiation-curable monomer, 15%pigment, 3% photoinitiator, and 2% UV light stabilizer by weight basedon weight of the coating, and c) an ink-receptive layer overlaying theradiation-cured layer, wherein the ink-jet recording medium has a watervapor transmission rate of no greater than 12 grams/100 square inches/24hours and a surface gloss of at least
 70. 13. The ink-jet recordingmedium of claim 1, wherein the ink-receptive layer comprises at leastabout 40% by weight water-soluble binder resin based on dry weight ofthe ink-receptive layer.
 14. The ink-jet recording medium of claim 13,wherein the water-soluble binder resin is selected from the groupconsisting of polyvinyl alcohols; poly(vinyl pyrrolidone);poly(2-ethyl-2-oxazoline); methylcellulose; poly(ethylene oxide); andcopolymers and mixtures thereof.
 15. The ink-jet recording medium ofclaim 13, wherein the ink-receptive layer further comprises awater-dispersible resin.
 16. The ink-jet recording medium of claim 1,further comprising a second ink-receptive layer (d) overlaying the firstink-receptive layer (c).
 17. The ink-jet recording medium of claim 1,wherein the dry coat weight of the ink-receptive layer is in the rangeof about 5 to about 50 grams/square meter.
 18. The ink-jet recordingmedium of claim 1, wherein the ink-receptive layer comprises poly(vinylpyrrolidone), poly(vinyl alcohol), polyurethane, and an opticalbrightener.
 19. The ink-jet recording medium of claim 1, wherein theink-receptive layer comprises methyl cellulose, polyethylene oxide,polyurethane, and alumina.
 20. The ink-jet recording medium of claim 1,wherein the first ink-receptive layer comprises poly(vinyl pyrrolidone),poly(vinyl alcohol), polyurethane, and an optical brightener, and thesecond ink-receptive layer comprises methyl cellulose, polyethyleneoxide, polyurethane, and alumina.
 21. An ink-jet recording mediumcomprising: a) a paper substrate having a first surface and a secondsurface, said second surface being opposite to the first surface, b) aradiation-cured layer overlaying the first surface of the papersubstrate, c) an ink-receptive layer overlaying the radiation-curedlayer, and d) a polymeric coating overlaying the second surface of thepaper substrate, wherein the ink-jet recording medium has a water vaportransmission rate of no greater than 12 grams/100 square inches/24 hoursand a first surface gloss of at least
 70. 22. The ink-jet recordingmedium of claim 21, wherein the polymeric coating comprises afilm-forming resin selected from the group consisting of polyvinylchloride; vinyl chloride copolymers; polyvinylidene chloride; vinylidenechloride copolymers; acrylates; methacrylates; polyvinyl acetate;polyacrylonitrile; polystyrene; and styrene copolymers.
 23. The ink-jetrecording medium of claim 21, wherein the polymeric coating is aradiation-cured layer formed by irradiating a coating comprising aradiation-curable oligomer and monomer, and photoinitiator.
 24. Theink-jet recording medium of claim 1, wherein the ink-jet recordingmedium has a surface gloss in the range of about 85 to about
 95. 25. Theink-jet recording medium of claim 1, wherein the ink-jet recordingmedium has a water vapor transmission rate of no greater than 5.0grams/100 square inches/24 hours.
 26. The ink-jet recording medium ofclaim 1, wherein the radiation-cured layer is cured by ultravioletlight.
 27. The ink-jet recording medium of claim 1, wherein theradiation-cured layer is cured by electron beam radiation.
 28. Anink-jet recording medium comprising: a) a paper substrate having asurface, b) a radiation-cured layer overlaying the surface of the papersubstrate, and c) a polymeric ink-receptive layer overlaying theradiation-cured layer, wherein the ink-jet recording medium has a watervapor transmission rate of no greater than 12 grams/100 square inches/24hours and a surface gloss in the range of 20 to
 70. 29. An ink-jetrecording medium comprising: a) a paper substrate having a surface, b) aradiation-cured layer overlaying the surface of the paper substrate, andc) a polymeric ink-receptive layer overlaying the radiation-cured layer,wherein the ink-jet recording medium has a water vapor transmission rateof no greater than 12 grams/100 square inches/24 hours and a surfacegloss less than
 20. 30. A continuous, in-line process for making anink-jet recording medium, comprising the steps of: a) applying aradiation-curable coating to a surface of a substrate material, b)irradiating the radiation-curable coating so that the coating undergoesa curing process, and ' c) applying an ink-receptive coating over theirradiated coating.
 31. The process of claim 30, wherein theradiation-curable coating is irradiated with ultraviolet light.
 32. Theprocess of claim 30, wherein the radiation-curable coating is irradiatedwith electron beam radiation.
 33. The process of claim 30, furthercomprising the step of treating the irradiated coating with a coronadischarge prior to applying the ink-receptive coating.
 34. The processof claim 30, further comprising the step of applying a coatingcomprising adhesion promoters over the irradiated coating prior toapplying the ink-receptive coating.
 35. The process of claim 30, whereinthe continuous, in-line process runs at a speed of at least about 60feet per minute.
 36. The process of claim 30, wherein theradiation-curable coating comprises a radiation-curable oligomer andphotoinitiator.
 37. The process of claim 30, wherein the ink-receptivecoating comprises at least about 40% by weight water-soluble binderresin based on dry weight of the ink-receptive layer.
 38. The process ofclaim 37, wherein the water-soluble binder resin is selected from thegroup consisting of polyvinyl alcohols; poly(vinyl pyrrolidone);poly(2-ethyl-2-oxazoline); methylcellulose; poly(ethylene oxide); andcopolymers and mixtures thereof.
 39. The process of claim 30, whereinthe weight of the irradiated coating is in the range of about 1 to about40 grams/square meter.
 40. The process of claim 30, wherein the weightof the ink-receptive coating is in the range of about 5 to about 50grams/square meter.
 41. A continuous, in-line process for making anink-jet recording medium, comprising the steps of: a) applying aradiation-curable coating to a surface of a substrate material, b)irradiating the radiation-curable coating so that the coating undergoesa curing process, and c) applying an ink-receptive coating over theirradiated coating to form an ink-jet recording medium having a watervapor transmission rate of no greater than 12 grams/100 square inches/24hours and a surface gloss of at least
 70. 42. A continuous, in-lineprocess for making an ink-jet recording medium, comprising the steps of:a) applying a radiation-curable coating to a first surface of asubstrate material having a first and second surface, b) irradiating theradiation-curable coating so that the coating undergoes a curingprocess, and c) applying an ink-receptive coating over theradiation-cured coating, and d) applying a polymeric coating to thesecond surface of the substrate material to form an ink-jet recordingmedium having a water vapor transmission rate of no greater than 12grams/100 square inches/24 hours and a first surface gloss of at least70.
 43. A continuous, in-line process for making an ink-jet recordingmedium, comprising the steps of: a) applying a radiation-curable coatingto a surface of a substrate material, b) irradiating theradiation-curable coating so that the coating undergoes a curingprocess, and c) applying an ink-receptive coating over the irradiatedcoating to form an ink-jet recording medium having a water vaportransmission rate of no greater than 12 grams/100 square inches/24 hoursand a surface gloss in the range of 20 to
 70. 44. A continuous, in-lineprocess for making an ink-jet recording medium, comprising the steps of:a) applying a radiation-curable coating to a surface of a substratematerial, b) irradiating the radiation-curable coating so that thecoating undergoes a curing process, and c) applying an ink-receptivecoating over the irradiated coating to form an ink-jet recording mediumhaving a water vapor transmission rate of no greater than 12 grams/100square inches/24 hours and a surface gloss less than 20.